Investigations of the size distribution and magnetic properties of nanoparticles of Cu2OSeO3

S J R Holt,J C Loudon,M R Lees,G Balakrishnan,A Štefančič

doi:10.1088/2053-1591/ac3aa8

S J R Holt, J C Loudon + Show 3 more

Open Access

https://doi.org/10.1088/2053-1591/ac3aa8

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Abstract

Skyrmions in confined geometries have been a subject of increasing interest due to the different properties that they exhibit compared to their bulk counterparts. In this study, nanoparticles of skyrmion-hosting Cu2OSeO3 have been synthesised using a precipitation method followed by thermal treatment. This enables us to produce nanoparticles whose mean size varies from tens of nanometers to a few micrometers by varying the temperature and duration of the thermal decomposition of the precursor. These sizes span the ∼63 nm diameter of skyrmions in Cu2OSeO3, allowing investigations into how the magnetic state changes when the size of the geometrical confinement is similar to and smaller than the size of an isolated magnetic skyrmion. AC susceptibility measurements performed on nanoparticles with a size distribution from 15 to 250 nm show a change in the magnetic phase diagram compared to bulk Cu2OSeO3.

Highlights

Magnetic skyrmions are topologically stable magnetic spin textures which have properties of quasi-particles [1]
In Lorentz transmission electron microscopy (LTEM) studies, thinning the sample dramatically increases the range of temperatures and magnetic fields over which skyrmions are stable [25]
We focus on the skyrmion-hosting material Cu2OSeO3, and the effects of three-dimensional geometric confinement of the skyrmions in nanoparticles of this material

Summary

Introduction

Magnetic skyrmions are topologically stable magnetic spin textures which have properties of quasi-particles [1]. At the surface of the skyrmion tube there is a change in the angle of magnetisation known as surface twists which have an additional Neel contribution [18, 20] These edge effects allow for the stabilisation of particle-like states such as chiral bobbers which manifest in a similar way to a skyrmion tube, but rather than the tube propagating all the way through the material, they end in a Bloch point [14, 15]. In Lorentz transmission electron microscopy (LTEM) studies, thinning the sample dramatically increases the range of temperatures and magnetic fields over which skyrmions are stable [25] This highlights the considerable effects that confinement along the axis of a skyrmion tube have on the stabilisation of skyrmions. Investigations of the size distribution and magnetic properties of nanoparticles of Cu2OSeO34

Experimental Details

Sample Preparation

Powder X-ray Diffraction

Discussion and Summary